This invention relates to a climate control system for controlling simultaneous cooling and heating functions in separate compartments with one compressor and one condenser.
Delivery trucks and trailers transporting temperature sensitive cargo include specially designed climate control systems. Typically, climate control systems such as refrigeration systems include a motor driving a compressor mounted outside of a cargo area. Refrigerant flows from the compressor through a condenser outside the cargo area, and to at least one remotely located evaporator unit. The refrigerant flows through an evaporator coil in the cargo area and back to the compressor. Cooling fans mounted as part of the evaporator blow air across the evaporator coils such that the air is cooled and expelled into the cargo area.
One type of climate control system is a direct drive unit where the compressor is driven by the engine of the motor vehicle during travel and when standing for brief periods. A standby compressor operates when it is not practical to run the motor vehicle engine. A simple system includes only one compartment maintained at a single temperature. However, cargo compartments having more than one temperature-controlled compartment are being increasingly put into service. Cargo trucks with two cargo areas capable of maintaining separate temperatures increases the efficiency of the delivery truck and has become increasingly in demand as home delivery service of fresh and frozen foods has gained increased popularity.
A direct drive system including one compressor and one condenser is not practical for applications requiring heating or defrost in one compartment and cooling in another compartment. This is so because the heating function requires the use of coolant at high-pressure, where the cooling function requires the use of coolant at low-pressure. Both high-pressure and low pressure cannot co-exist in the same common compressor suction line.
For this reason it is desirable to design a system and method to concurrently heat one compartment and cool another with a single compressor and condenser.
An embodiment of a climate control system for a container truck of this invention includes a compressor, a condenser and at least two evaporator assemblies, capable of heating in one compartment and cooling in another.
The primary motive engine of the motor vehicle drives the compressor during most operating periods, and a standby compressor is provided for use during periods when it is not practical to operate the engine of the motor vehicle. The evaporator assemblies are mounted within separate compartments of the container and are both supplied coolant from the common condenser. The system includes a liquid line communicating coolant in a liquid state from the condenser to each of the evaporators and a hot gas bypass circuit that communicates hot gas from the compressor to each of the evaporators. Hot gas from the bypass circuit provides for heating of the specific compartment and for defrost of each of the evaporators. Coolant flow from the condenser is controlled by a liquid solenoid valve and from the bypass circuit by a hot gas solenoid valve.
Coolant exiting each of the evaporators is routed through a common circuit to the compressor. The common line is held at a predetermined coolant pressure, regardless of the coolant pressure at each of the evaporators by way of two individual crankcase pressure regulators. Each of the evaporators includes a crankcase pressure regulator such that coolant pressure within the evaporator does not vary the pressure within the common coolant line back to the compressor. The system of the subject invention is capable of cooling in one compartment with one evaporator and heating in another compartment with the other evaporator. This is accomplished by the use of the separate crankcase regulators for each evaporator. With separate crankcase regulators, beating and cooling with a common compressor is possible because the pressure in the common suction line can not be at two different pressures.
In operation, a controller controls each of the solenoid valves of the system to obtain the desired temperature. The controller selectively opens or closes either the liquid or the hot gas valve to obtain a desired temperature. The controller of this invention includes an automatic mode and a priority mode that governs how the various valves are actuated to obtain the desired compartment temperature.
The climate control system of this invention efficiently manages the actuation of the various valves to control thermostatically different temperatures in different compartments.